Wednesday, February 15, 2017

Human vision is more sensitive during physical activity

It's universally accepted that the
benefits of exercise go well beyond fitness, from reducing the risk of disease
to improving sleep and enhancing mood. Physical activity gives cognitive
function a boost as well as fortifying memory and safeguarding thinking skills.

But can it enhance your vision? It
appears so.

Intrigued by recent findings that
neuron firing rates in the regions of mouse and fly brains associated with
visual processing increase during physical activity, UC Santa Barbara
psychologists Barry Giesbrecht and Tom Bullock wanted to know if the same might
be true for the human brain.

To find out, they designed an
experiment using behavioral measures and neuroimaging techniques to explore the
ways in which brief bouts of physical exercise impact human performance and
underlying neural activity. The researchers found that low-intensity exercise
boosted activation in the visual cortex, the part of the cerebral cortex that
plays an important role in processing visual information. Their results appear
in the Journal of Cognitive Neuroscience.

"We show that the increased
activation -- what we call arousal -- changes how information is represented,
and it's much more selective," said co-author Giesbrecht, a professor in
UCSB's Department of Psychological and Brain Sciences. "That's important
to understand because how that information then gets used could potentially be
different.

"There's an interesting
cross-species link that shows these effects of arousal might have similar
consequences for how visual information is processed," he continued.
"That implies the evolution of something that might provide a competitive
advantage in some way."

To investigate how exercise affects
different aspects of cognitive function, the investigators enlisted 18
volunteers. Each of them wore a wireless heart rate monitor and an EEG
(electroencephalogram) cap containing 64 scalp electrodes. While on a
stationary bicycle, participants performed a simple orientation discrimination
task using high-contrast stimuli composed of alternating black and white bars
presented at one of nine spatial orientations. The tasks were performed while
at rest and during bouts of both low- and high-intensity exercise.

The scientists then fed the recorded
brain data into a computational model that allowed them to estimate the
responses of the neurons in the visual cortex activated by the visual stimuli.
They analyzed the responses while participants were at rest and then during
low- and high-intensity exercise.

This approach allowed them to
reconstruct what large populations of neurons in the visual cortex were doing
in relation to each of the different stimulus orientations. The researchers
were able to generate a "tuning curve," which estimates how well the
neurons are representing the different stimulus orientations.

"We found that the peak response
is enhanced during low-intensity exercise relative to rest and high-intensity
exercise," said lead author Bullock, a postdoctoral researcher in UCSB's
Attention Lab. "We also found that the curve narrows in, which suggests a
reduction in bandwidth. Together, the increased gain and reduced bandwidth
suggest that these neurons are becoming more sensitive to the stimuli presented
during the low-intensity exercise condition relative to the other conditions."

Giesbrecht noted that they don't know
the mechanism by which this is occurring. "There are some hints that it
may be driven by specific neurotransmitters that increase global cortical
excitability and that can account for the change in the gain and the increase
in the peak response of these tuning profiles," he said.

From a broader perspective, this work underscores the
importance of exercise. "In fact, the benefits of brief bouts of exercise
might provide a better and more tractable way to influence information
processing -- versus, say, brain training games or meditation -- and in a way
that's not tied to a particular task," Giesbrecht concluded.